Arteficial horizon and bank indicator for aircraft trainers



Aug. 14, 1945. 2,381,872

ARTIFICIAL HORIZON AND BANK INDICATOR FOR AIRCRAFT TRAINERS Filed Aug.17, 1943 2 Sheets-Sheet R m w w CI. BY

m A U B A TTORNEY C. l. BAKER Aug. '14, 1945.

ARTIFICIAL HORIZON AND BANK INDICATOR FOR AIRCRAFT TRAINERS 2Shets-Sheet 2 Filed Aug. 1'7, 1943 205k 546E 1 tom 35% kuwmmou INVENTORC l BAKER A TTORNEY Patented Aug. 14, 1945 ARTIFICIAL HORIZON AND BANKINDI- CATOR FOR AIRCRAFT TRAINERS Clarence I. Baker, Elizabeth, N. J.,assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application August 17, 1943,Serial No. 498,913

7 Claims.

Thisinvention relates to an artificial horizon and bank indicator foruse in an aircraft trainer.

For the purpose of training the pilot of an aircraft to conduct a flightby the observation of instruments. ground trainers have been developedwhich are provided with the controls and flight recording instrumentswhich would be found in an actual aircraft. By operating the controls apilot may simulate an actual flight and observe the response of theinstruments to his operation of the controls and yet the trainer doesnot leave the ground. A trainer of this type materially reduces theactual air flight training in an actual aircraft and reduces the hazardsto both the pilot and to the aircraft during the preliminary trainingperiod.

Among the instruments which are required to give the pilot undertraining the simulation of actual flight is an artificial horizoninstrument which is responsive to the operation of the yoke or elevatorcontrol to indicate to the pilot whether in response to his operation ofthe elevator he is simulating a climbing. a level or a descending flightand which is also responsive to the operation of the rudder pedals orrudder control or to the aileron control or to both to indicate to thepilot the direction and degree of bank of the simulated flight.

The object of the invention is to provide an instrument of thischaracter which is simple in construction, reliable in operation, whichrequires a minimum of energy for its operation and which may be operatedin an aircraft trainer in simulation of the operation of the usualgyroscope controlled horizonand bank indicator.

To attain thisobject the face of the casing of the instrument isprovided with the usual bank or turn scale and with a verticallyadjustable silhouette of an aircraft. Positioned back of the scale andvisible through the face of the casing is a background disc of the usualtype, the lower portion of which is colored to represent the ground andthe upper portion of which is colored to denote the sky. The bankindicator pointer is secured to the upper edge of the background disc ina position to cooperate with the bank or turn scale when the backgrounddisc is rotated.

The background disc is secured to the forward end of a carriage mountedfor rotation on a horizontal axis aligned with the center of the bankand turn scale. To enable this carriage to be freely rotated it isjournaled in ball bearings. To rotate the carriage a gear is secured tothe rear end thereof which is driven by a pinion secured to the shaft ofa motor of the self-synchronous type.

A bar simulating the horizon lies in front of the background disc and ismovable in a plane parallel to the surface of such disc. For thispurpose the horizon bar is provided with a portion extending rearwardlywhich is pivoted near its rear end to the carriage. This horizon bar isoscillatable about its pivot by a crank pin carried by a gear which pinslidably engages the rearwardly extending portion of the horizon bar.This gear is rotatable on a stub shaft secured to the carriage, by apinion rotatable on a second stub shaft also secured to the carriage.The pinion is in turn operated by a rack which is attached to one end ofa rod slidable in an axial hole extending through the rear ball bearing.The other end of the rod is connected by a swivel coupling to a secondrack operable by a second motor of the self-synchronous type.

Through the operation of the two motors, the background disc and horizonbar are tiltable with respect to the silhoutte to give the illusion thatthe trainer is banked for a turn and the horizon bar is depressed orraised to give the illusion that the trainer is either climbing ordiving.

For a clearer understanding of the invention,

reference may now be had to the following detailed description thereoftaken in connection with the accompanying drawings in which:

Fig. 1 is a top plan view of the horizon and bank indicator partly incross-section;

Fig. 2 is a side elevational view partly in crosssection;

Fig. 3 is a front view of the indicator drawn to a reduced scale showingthe position of the horizon bar to denote a climb;

Fig. 4 is a similar front view of the indicator showing the position ofthe horizon bar to denote level flight;

Fig. 5 i a similar front view of the indicator showing the position ofthe horizon bar to denote adive; and

Fig. 6 is a similar front view of the indicator showing the position ofthe horizon bar to denote a correctly banked turn to the right.

The artificial horizon and bank indicator in accordance with the presentinvention is provided with a supporting frame comprising a substantiallycircular front wall I having a circular opening 2 therein, tworearwardly extending and cylindrically contoured arms 3 and 4 and across member 5 joining the rear ends of the arms and lying in a planeparallel to the front wall I. The frame is also provided near its frontwall with a horizontally extending post 5 which serves to support a ballbearing in which the forward end of a carriage I is ioumaled.

Secured by screws 5 to the front wall I of the supporting frame, is adial ring 3 of substantially circular shape provided with fourdiametrically extending portions III each having a threaded hole lltherein for receiving a screw by which the instrument may be supportedon the instrument panel of the trainer. The dial ring 3 is provided withan opening I! therethrough of substantially the shape disclosed in Fig.3 providing at its lower end a post I! for supporting a miniaturerepresentation l4 of the rear of an aircraft.

The ring I is provided with a shoulder l5 adiacent the edge of theopening I: upon which is seated a mask It. The upper half of the mask isgraduated from to 90 degrees to the right and left of the center indexI! as best shown in Fig. 3 with the 90 degree markings of the scaleswidened as at It and I and positioned to be in alignment with thehorizon bar when the trainer is being operated to simulate level flight,as best shown in Fig. 4. The lower part of the mask is shaped as shownat 26 in Fig. 3 and is bent outwardly at 2| and 22 to afford space forthe aircraft silhouette l4 and the adjusting mechanism therefor. Thering 5 is also provided with an additional shoulder 23 in which isseated a cover glass 24 held in place by a spring retaining or bezelring 25. The aircraft silhouette I4 is vertically adjustable and forthis-purpose is provided with downwardly extending rack portion 26 whichmeshes with a pinion 21 rotatably supported on the post I 3 and having agear 28 secured thereto and positioned at the rear of the post l3. Gear26 may be rotated by the pinion 36 through an idler gear 23 meshed withthe gear 28 and with the pinion 35. The pinion 30 is secured to theinner end of a spindle 3| journaled in a bearing formed in the loweredge of the ring 9. A knob 32 is secured in any desired manner to theouter end of the spindle, for example, the knob may be molded upon athimble 33 which thimble may be secured to the spindle by a set screw.When the knob 32 is turned to rotate the pinion 30, the rotation of thepinion is communicated throu h the gears 25. 25 and 21 to cause thesilhouette to be raised or lowered as desired.

The post 5 is provided adjacent to its inner end with a hole in which ispositioned a front ball bearing assembly 34, the axial center of whichis aligned with the center of the opening 2 of the supporting frame, andthe cross member 5 is also provided with a hole in which is positioned arear ball bearing assembly 35, the axial center of which is aligned withthe center of bearing assembly 34. The inner raceways of these bearingassemblies are disposed on cylindrically formed portions extending fromthe end members 35 and 31 of the carriage I. These end members areJoined by a. face plate portion 38 strengthened on its rear face-by aweb 33.

The cylindrical portion of the front end member 36 of the carriageextends forwardly beyond the post 5 as shown at 45 to support thebackground disc The disc 4| is circular in outline but is dishedcylindrically as .best disclosed in Fig. 2 and is secured at its centerto a split hub 42 which is secured by a suitable clamping screw 43 tothe extension 45 of the carriage, whereby the disc is rotated about theaxis of the instrument when the carriage is rotated. The upper portionof the front face of the disc is colored to represent the sky and thelower portion of the front face of the disc is colored to denote theground. Thus as the trainee views the face of the instrument as it ismounted on his instrument panel, he sees the miniature aircraft l4silhouetted against the background disc 4|,

Secured to the upper edge of the disc 4! and extending through theopening 2 in the supporting frame and the opening I2 in the dial ring 9is a pointer 44. This pointer has its outer end turned upwardly in theplane of the mask l5 to be movable upon the rotation of the carriage andbackground disc along the inner edge of the scale on the mask l6. If thetrainer is operated to simulate level flight or a climbing or divingcondition with no bank for a turn, the pointer 44 will be aligned withthe center index ll of the scale as disclosed in Figs. 3, 4 and 5. If,however, the trainer is operated to simulate abanked condition, thepointer will move over the scale to the left or right of the centerindex 11 to indicate the degree and direction of the bank. Fig. 6

shows the pointer 44 moved to indicate approximately a 30 degree bankfor a ri ht turn.

The carriage I is rotatable in the ball bearing assemblies 34 and 35 bya gear 45 mounted on a circular shoulder of the end member 31 of thecarriage and secured thereto as by swaging, which gear is driven by apinion 46 mounted on the shaft 41 of a driving motor 48. The motor 43 isof the self-synchronous type which is coupled electrically with asynchro-transmitter driven by one of the motor control circuits of thetrainer.

' This motor is provided with a mounting plate 49 by which it is securedto the cross member 5 of the supporting frame by lag screws 50.

Secured to the face plate 36 of the carriage I is a bracket 5| havingtwo parallelly disposed upwardly extending cars 52 between which a bar53 is pivoted by a pivot screw 54. The bar 53 extends toward the frontof the instrument, is bent outwardly at 55, as best shown in Fig. 1, toa point outside the edge of the background disc 4i and is then bent atright angles to form a horizon bar 56 which extends horizontally acrossthe face of the background disc but sufficiently spaced therefrom to befreely movable in a cylindrical plane parallel to the face of the disc.The bar 53 is balanced on the pivot screw 54 by an adjustablecounter-weight 51 movable along the bar and secured thereto by the setscrew 58.

For oscillating the bar 53 about its pivot screw, the bar slidablyextends through holes in the parallelly disposed ears 5!! in a crank pin56 pivotally secured to the spur gear 6!. This spur gear is rotatable ona stub shaft 52 secured to the face plate 33 of the carriage by the nut53. As gear 6| is rotated the crank pin 60 moves the rod 53 up or downfrom the center position disclosed in Fig. 2 depending upon thedirection of rotation of the gear, thereby raising or lowering thehorizon bar 56 with respect to the silhouette l4 and the end-of-scalemarkings I 8 and I9. Gear 6| is cut away as indicated at 64 in Fig. 2 tobalance the additional weight added thereto by the crank pin 60.

The gear 6| is driven by a pinion 65 rotatably mounted on another stubshaft secured to the face plate 38 in the same manner as the stub shaft62. This pinion in turn is driven by a slidable rack 66. The rack 66 isheld in mesh with the pinion 65 and guided in its movement by a groovedroller 61 which is rotatably mounted on another stub shaft 66 secured tothe face plate 38 .by the nut 69. On end of the rack 56 terminates in asleeve 10 by which it is secured to one end required to handle a minimumload, the parts of of a cylindrical driving rod H. The rod H extendsfreely through a hole 12 drilled axially through the cylindricalextension of the end member 81 of the frame on which the ball bearingassembly 35 is mounted, and through a hole in the cross member of thesupporting frame and terminates in a headed portion enclosed in thecasing 18 of a swivel coupling of well-known construction, bestdisclosed in Fig. 2. Extending from the other side of the swivelcoupling is a rack H,

For operating the rack a motor is provided having a. pinion 16 securedto its rotor shaft ll. The motor is Provided with a mounting plate 19which is supported on posts 18 riveted or otherwise secured to amounting plate 95 and is secured to such posts by the screws 80. Theplate 95 is in turn secured to a bracket 8!, formed integrally with thecross member 5 of the supporting frame, by the screws 82.

The rack 14 is held in mesh with the pinion 16 and in alignment with thedriving rod 1| by grooved rollers 83 which are rotatably mounted on stubshafts 84 secured to the mounting plate 95. Th rollers are held on saidshafts by the nuts 85.

The instrument is protected from dust and mechanical injury by acylindrical cover 86 having a rear end closure 81 welded thereto andhaving a clamping ring 88 secured, as by welding, to its forward edge.The cover is secured to the front wall I of the supporting frame by thelag screws 89. A multi-terminal connector 90 is secured to the cover 86by screws 9| to afford means for extending operating circuits to themotors 48 and 15.

The knob 92 and index plate 93 have no utility in the instrument of thepresent invention but since they do form a useful part of the horizonand bank indicator appearing on the instrument panel of a regularaircraft, they are retained in order that when the trainee looks at theinstrument, it will have exactly th same appearance as the instrument ofa regular aircraft.

Through the operation of the motor 15 under the control of a motorcontrol circuit -of the trainer in which the instrument is installed inresponse to the operation of the controls of simulate level flight, aclimbing flight or a diving flight, the rack 14 is operated either tothe left or to the right and through th connecting rod H, the rack 66,the pinion 64 and the gear 6|, causes either a depression or a raisingof the horizon bar 56. If the bar 56 is depressed as disclosed in Fig. 3below the silhouette H, a. climb is denoted. If the bar assumes theposition disclosed in Fig 4 in alignment with the silhouette a levelflight is denoted and if the bar is raised as disclosed in Fig. 5 abovethe silhouette a dive is denoted.

As previously described the operation of the motor 48 under the controlof a motor control circuit of the trainer in response to the operationof the controls to simulate a banked turn, rotates the carriage throughthe operation of the gears 45 and 46. Such turning is unhampered by theengagement of the rack 14 with the pinion 16 and rollers 83 through theprovision of the swivel coupling 13. The turning of the carriage iseffective to turn the background disc 4|, the pointer 44 and the horizonbar 56. For a correct bank for a right turn, the horizon bar will assumea position such as is illustrated in Fig. 6.

Since self-synchronizing motors of the type employed most accuratelyfollow the operation of their driving synchro-transmitters when they arethe instrument movable thereby are made as light as possible, made tomove freely as by the use of the ball bearing assemblies 34 and 35 andby the guiding rollers 61 and 83 and the parts are carefullycounter-balanced as by the provision of the counter-balancing weight 51for counter-balancing the horizon bar 56, by the provision of the holes84 in the gear 6| for counter-balancing the crank pin 60 and by theprovision of the counterbalanced weight 96 threaded upon the stud 91extending from the carriage l and held in its 8djusted position by theset screw 98, which balances the carriage I and the mechanism carriedthereby.

As an alternative construction, the rod H could be made slightly largerin diameter and provided with circumferentially cut rack teeth on eachend thereof, the rack teeth on one end meshing with the pinion 64 andthe rack teeth on the other end meshing with the motor pinion 16. Withthis type of construction the swivel coupling 13 could be omitted.

What is claimed is:

1. In a horizon and bankindicator for an aircraft trainer, a frame, a"bank indicating scale secured thereto, a background disc, a pointersecured to said disc for cooperation with said scale, a pivoted horizonbar positioned in front of said disc, a motor for rotating said disc andsaid horizon bar together, whereby said pointer is moved with respect tosaid scale, and a second motor for moving said horizon bar about itspivot independently of said disc to move said bar in a plane parallel tothe surface of said disc.

2. In, a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving motor mounted on said frame, a bankindicating scale secured to said frame, a carriage pivotally mounted in'said frame, a background disc having a bank pointer secured theretocarried by said carriage, gearing driven by said first motor forrotating said carriage to move said disc and pointer with respect tosaid scale, a horizon bar pivoted on said carriage, and means driven bysaid second motor for moving said horizon bar over the face of saidbackground disc comprising a gear rotatably mounted on said carriage, acrank pin pivotally secured to said gear and slidably engaged with saidbar, a pinion gear rotatably mounted on said carriage and in mesh withsaid first gear and a rack member slidably extending through a holeformed axially in a pivotal mounting of said carriage and in mesh withsaid pinion gear and with a pinion on the shaft of said second motor.

3. In a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving motor mounted on said frame, a bankindicating scale secured to said frame, ball bearing assemblies mountedin said frame, a carriage journaled in said bearing assemblies, abackground disc having a bank pointer secured thereto carried by saidcarriage, gearing driven by said first motor for rotating said carriageto move said disc and'pointer with respect to said scale, a horizon barpivoted on said carriage, and means driven by said second motor formoving said horizon bar over the face of said background disc comprisinga gear rotatably mounted on said carriage, a crank pin pivotally securedto said gear and slidably engaged with said bar, a pinion gear rotatablymounted on said carriage and in mesh with said first gear, and a rackmember slidably extending through a hole formed in mesh with said piniongear and with a pinion gear on the shaft of said second motor.

4. In a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving motor mounted on said frame, a bankindicating scale secured to said frame, a carriage pivotally mounted insaid frame, a background disc having a bank pointer secured theretocarried by said carriage, gearing driven by said first motor forrotating said carriage to move said disc and pointer with respect tosaid scale, a horizon bar pivoted on said carriage, and means driven bysaid second motor for moving said horizon bar over the face of saidbackground disc comprising a gear rotatably mounted on said carriage, acrank pin pivotally secured to said gear and slidably engaged with saidbar, a pinion gear rotatably mounted on said carriage and in mesh withsaid first gear, a first rack slidably mounted on said carriage and inmesh with said pinion gear, a second rack operable by a pinion on theshaft of said second motor and a rod connecting said rack and extendingthrough a hole formed axially in a pivotal mounting of said carriage.

5. In a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving motor mounted on said frame, a bankindicating scale and an aircraft silhouette secured to said frame, acarriage pivotally mounted in said frame, a background disc having abank pointer secured thereto carried by said carriage, gearing driven bysaid first motor for rotating said carriage to move said disc andpointer with respect to said scale, a horizon bar pivoted on saidcarriage, and means driven by said second motor for moving said horizonbar over the face of said background disc and with respect to saidsilhouette comprising a gear rotatably mounted on said carriage, a crankpin pivotally secured to said gear and slidably engaged with said bar, apinion gear rotatably mounted on said carriage and in mesh with saidfirst gear, a first rack slidably mounted on said carriage and in meshwith said pinion gear, a second rack operable axially through one end ofsaid carriage and axby a pinion on the shaft of said second motor and arod connecting said rack and extending through a hole formed axially ina pivotal mounting of said carriage.

6. In a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving otor mounted on said frame, a bank indicatingscale secured to said frame, a carriage pivotally mounted in said frame,a background disc having a bank pointer secured thereto carried by saidcarriage, gearing driven by said first motor for rotating said carriageto move said disc and pointer with respect to said scale, a

horizon bar pivoted on said carriage, and means driven by said secondmotor for moving said horizon bar over the face of the background disccomprising a gear rotatably mounted on said carriage, a crank pinpivotally secured to said gear and slidably engaged with said bar, apinion gear rotatably mounted on said carriage and in mesh with saidfirst gear, a first rack slidably mounted on said carriage and in meshwith said pinion gear, a rod connected to said rack and extending freelythrough a hole formed axially in a pivotal mounting of said carriage, asecond rack operable by a pinion on the shaft of said second motor, anda swivel coupling between said rod and said second rack for permittingrotation of said carriage without hindrance from said second rack.

7. In a horizon and bank indicator for an aircraft trainer, a frame, afirst and a second driving motor mounted on said frame, a bank indicating scale secured to said frame, a carriage pivotally mounted in saidframe, a background disc having a bank pointer secured thereto carriedby said carriage, gearing driven by said first motor for rotating saidcarriage to move said disc and pointer with respect to said scale, ahorizon bar pivoted on said carriage, means driven by said second motorfor moving said horizon bar over the face of said background disc andadjustable weights for counter-balancing said carriage and said horizonbar for enabling the movement thereof with the minimum expenditure ofenergy by said motors.

CLARENCE I. BAKER.

